Whether PROMICE-AWS-data-issues is found depends on where get_l3 is run: should be changed for absolute path

[BaptisteVandecrux]

Since github_data_issue.py look for flag and adjustment CSVs at

pypromice/src/pypromice/qc/github_data_issues.py

Lines 19 to 20 in 6ad7ee7

	def flagNAN(ds_in,
	flag_dir='../PROMICE-AWS-data-issues/flags'):

whether it finds it or not depends on where pypromice is run.

I noticed that when because l3_reprocess.py was running fine but l3_processor.py could not find the flag files. This is because l3_processor.py was running get_l3 in the ./pypromice/src/pypromice folder and the relative path to the flag files was broken.

To prevent this from re-happening, I suggest that get_l3 would give the absolute paths of the flags and adjustment files instead of the relative path.

I also suggest that l3_reprocess.py and l3_processor.py should only make CLI calls containing absolute paths (instead of switching from folder to folder with cd).

[BaptisteVandecrux]

since #294, The location of the PROMICE-AWS-data-issues folder is now a command line input:
https://github.com/GEUS-Glaciology-and-Climate/pypromice/blob/main/src/pypromice/process/get_l2.py

Atm if not provided, a relative path is still used. In the future the path to PROMICE-AWS-data-issues will be required.